siblings is package{

  siblings is relation of {
    ("john", "peter");
    ("john", "mary");
    ("mary", "peter");
    ("mary","john");
    ("peter","john");
    ("peter","mary")};
  
  ages has type relation of ((string,integer));
  ages is relation{
    ("john",10);
    ("peter",12);
    ("mary",8);
  };
  
  JS is all A where ("john",S) in siblings and (S,A) in ages order by A;
  
  JSS is all (S,A) where ("john",S) in siblings and (S,A) in ages order by A using (<);
  
  main() do {
    logMsg(info,"John's siblings' ages are: $JS");
    logMsg(info,"John's siblings are: $JSS");
  }
}